Electric plug with both removable and pivotable ground pins

ABSTRACT

A male electric plug is of the type having a first grounding means and also a second grounding means. The first grounding means is an elongated ground pin member movable in a grounded socket member and the second grounding means is an inflexible element mounted on, integral with and grounded with one of the members for connection to an outlet plate. In one form both grounding means are pins freely slidable in grounded sockets. In another form the first grounding means is a pin pivotable in a socket and an integral tail on the pin is the second grounding means.

United States Patent 1191 Jenkins Feb. 12, 1974 1 ELECTRIC PLUG WITH BOTH 3,685,000 8/1972 Robbins 339/14 P REMOVABLE AND PIVOTABLE GROUND 2,986,718 5/1961 Bender 339/14 RP PINS 1 Primary Examiner-Marvin A. Champion [76] Inventor: Robert L. Jenkins, P.O. Box 115, Assistant Examiner Robert A. Hafer North Salem 03073 Attorney, Agent, or FirmPearson & Pearson [22] Filed: Jan. 3, 1972 211 Appl. No.: 214,566 [57] ABSTRACT A male electric plug is of the type having a first 52 us. Cl 339/14 P, 339/31 R gmundng mean? and Secmd gmmdmg The first grounding means is an elongated ground pm [51} Int. Cl HOlr 3/06 b bl d d k b d 58 Field of Search 339/14 R, 14 RP, 14 P, 31, mm er 6 3 the second grounding means 1s an inflexible element 339/32, 33, 154,155, 196

mounted on, mtegral with and grounded with one of [56] References Cited the members for connection to an outlet plate. In one form both grounding means are pins freely slldabl e 1n UNITED STATES PATENTS v grounded sockets. In another form the first grounding 2,984,808 5/1961 Bender 339/31 R means is a pin pivotable in a socket and an integral tail 3,299,390 1/1967 Eckelkamp 339/14 RP on h i i the second grounding means 3,531,757 9/1970 Alden 339/14 P 3,381,258 4/1968 Becker 339/14 P 9 Claims, 6 Drawing Figures ELECTRIC PLUG WITH BOTH REMOVABLE AND PIVOTABLE GROUND PINS BACKGROUND OF THE INVENTION Three-prong electric male plugs are common and usually consist of a pair of male prongs connected to a pair of wires in a cable and a third prong, or pin, connected to a ground wire in the cable. It is most disconcerting to attempt to use an electric tool or appliance, especially in older buildings, only to find that the female outlet has no third hole for the ground pin of the tool. Adapters are commercially available, but usually not on hand when needed. In such situations, workmen have been observed breaking off the third prong in anger or desperation.

It has heretofore been proposed to construct such three-prong plugs, with the ground pin pivotable out of the way, as in U.S. Pat. Nos. 2,984,808 of May 16, 1961 to Bender, 2,986,718 of May 30, 1961 to Bender, 3,134,631 of May 26, 1964 to Whalen or 3,144,287 of Aug. 1 l 1964 to Morse, and many other patents. It has also been proposed to use an axially slidable ground pin which advances or retracts, while captive on a pivot pin, as in U.S. Pat. No. 3,299,390 to Eckelkamp of Jan. 17, 1967, or which advances or retracts in a sleeve from the front face of the plug, as in U.S. Pat. No. 3,025,486 to Falconer of Mar. 13,1962, and 3,531,757 to Alden of Sept. 29, 1970, 3,495,205 to Ricci of Feb. 10, 1970, and many other patents.

SUMMARY OF THE INVENTION In this invention, reliance is not placed on a single grounding means on the plug, nor is the plug provided with two grounding means which cannot be removed, as in U.S. Pat. No. 3,381,258 to Becker of April 30, 1968. Instead, the plug of this invention preferably comprises an elongated ground pin, greater in length than the length of the plug, and freely slidable in a full axial length, conductive socket in the plug so that one end projects from the front face and the other end projects from the rear face of the plug. Thus, when not to be used, the ground pin is slidably removable from the rear of the plug. In addition, the electric conductive element inside the plug not only includes the above mentioned socket but also includes a second, dead-end socket which slidably receives one end of a second ground pin, threaded into the screw hole of the outlet plate so that ground is achieved, even when the first ground pin is removed.

Alternatively, in another embodiment, the structure of the plug of the invention includes a ground pin having one end pivoted in a yoke, or socket, of the conductive element to retract down into a groove in the front face of the plug in a manner similar to prior art devices, but the pivotable ground pin includes an integral conductive tail. When the pin is normal to the plug face, the tail is screwed to the conductive element to hold the pin in operating position. When the tail is unfastened and the pin folded down into the groove, the tail pivots outwardly to a position in which it meets the attachment screw hole of the outlet plate and may be grounded by the attachment screw to assure a ground.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation in half section of one embodiment of the plug of the invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a side elevation in half section showing the two pin sockets in the ground, conductive element.

FIG. 4 is a side elevation in half section of the other embodiment of the invention.

FIG. 5 is a detail view of the ground pin and integral tail, and

FIG. 6 is a detail view of the conductive element and I its yoke, or socket, for the ground pin.

As shown in FIGS. 1 through 3 of the drawing, the male electric plug 25 of the invention includes a plug body 26 of any convenient non-conductive material, such as rubber, having a front face 27, a rear face 28 and being of a predetermined axial length 29, such as about one inch. Plug 25 includes a pair of male contact prongs 31 and 32 of metal connected to two wires 33 and 34 of the three-wire, electric cable 35, the third wire 36 thereof being a ground wire connected to electric conductor 37.

The plug 25 includes first grounding means 41 comprising the full axial length conductive socket 42 of conductor 37, which is preferably a hollow metal cylindrical tube, and the first elongated ground pin 43 which is slidably received in socket 42. Ground pin 43 is also cylindrical and includes one end 44 which projects beyond front face 27 to enter the ground hole 45 of the outlet plate 46, and an enlarged-head 47, at the other end, projecting beyond rear face 28 to serve as a finger grip for rearward withdrawal of the pin 43 from the plug. It will be noted that pin 43 is of substantially greater length than the axial length 29 of the plug, for example about two inches. Socket 42 is preferably split at 48, flared at 49 and open at both ends 51 and 52.

In the embodiment of FIGS. 1 through 3, the second grounding means 54 comprises a second conductive socket 55 integral with, and mounted on, the conductor 37 and having a closed split end 56 and an open end 57 in the front face 27 of plug 25. A second ground pin .58 includes a smooth end 59 slidably fitting within second socket 55, a central enlarged tapered portion 61 and a threaded end, or screw, 62, threadedly engaged in the threaded screw hole 63 of outlet plate 46.

It will be seen that grounding of any appliance or tool attached to cable 35 is doubly assured when both grounding means 41 and grounding means 54 are operable and continues to be assured through grounding means 54, when the outlet plate 46 has no ground hole and pin 43 is removed from the plug.

In FIGS. 4 through 6 another embodiment of the invention is illustrated in which the first grounding means 64 of the male electric plug 65 comprises the electric conductor 66 connected to the ground wire 67 and having a yoke, or socket, 68 in which the elongated ground pin 69 is pivotable on pivot pin 71. Pin 69 includes an integral tail 72 having an aperture 73 for a machine screw 74 threaded in plug body 75 to retain the pin 69 in a position normal to front face 76 and in parallelism with the male contact prongs 77 and 78. Front face 76 is provided with a groove 79, extending transversely of the face between the male prongs to receive the pin 69, when screw 74 is unfastened and the ground pin 69 pivoted down out of the way into recumbant position in the groove 79.

The second grounding means 81 of this embodiment comprises the tail 72, with its aperture 73 and machine screw 74, which pivots outwardly into position opposite the threaded hole 63 of outlet plate 46 when pin 69 is in the groove, so that the screw 74 may be threaded into hole 63 and maintain a ground for the tool or appliance.

As best shown in FIG. 5, ground pin 69 is preferably hollow and contains a ball 82 spring biased by a coil spring 83 against pivot pin 71, whereby the ground pin is resiliently urged into rccumbant position and into normal position, and yieldably locked in each said position.

In the embodiment of FIGS. 1 through 3 the first grounding means 41 comprises the pin member 43 and the grounded socket member 42, while the second grounding means comprises the second socket 55 which is an inflexible element immovably mounted on, integral with and grounded with one of the members of the first grounding means, namely with the grounded socket member 42.

In the second embodiment of FIGS. 4 through 6, the first grounding means 64 comprises the pin member 69 and the grounded socket member 68, while the second grounding means 81 comprises the tail 72 which is an inflexible element immovably mounted on, integral with and grounded with one of the members of the first grounding means, namely the pin member 69.

I claim:

1. A male electric plug having an electric ground, said plug comprising:

a plug body having a pair of male contact prongs projecting from one face thereof and having a threewire electric cable secured in another face thereof, each of said prongs being connected to one of the wires of said cable;

first grounding means including a pin receiving socket member in said body, an elongated ground pin member mounted to move relative to said socket and an electric conductor connecting one of said members to the third wire of said cable; and

second grounding means, including an inflexible element immovably mounted on, integral with and grounded to one of said members of said first grounding means; and including a threaded fastening screw directly and inflexibly connecting said element to a female electric outlet.

2. A male electric plug as specified in claim 1, wherein:

said pin receiving socket member is a conductive sleeve extending through said body from said one face to said another face;

said ground pin is freely and slidably received in said sleeve for complete withdrawal from said plug body; and

said element of said second grounding means is a dead-end conductive sleeve integral with said pin receiving socket member.

3. A male electric plug as specified in claim 1,

wherein:

said element of said second grounding means comprises a second pin receiving socket and said threaded fastening screw is a second ground pin having one end slidably received in said socket and the other end threaded to threadedly engage in the screw hole of said female electric outlet.

4. A male electric plug as specified in claim 1,

wherein:

said pin receiving socket member is a hollow metal cylinder open at each opposite end for slidably receiving said ground pin; and

said element of said second grounding means is a second socket closed at one end for slidably receiving a second ground pin, forming one end of said fastening screw. 5. A male electric plug as specified in claim 1, wherein:

said pin receiving socket member includes a groove in said body extending transversely of said one face between said male prongs, said ground pin member is pivoted at one end to said electric conductor to move from a position normal to said one face and parallel to said prongs to a rccumbant position in said groove; and

said element of said second grounding means is an integral tail on said pin.

6. A male electric plug as specified in claim I,

wherein:

said body includes a groove in said one face, said ground pin member is pivotable on said conductor from a position within said groove to a position normal to said one face; and

said ground pin member includes an integral tail, having a threaded hole therein, for receiving said screw to affix said tail to said conductor in said normal position and to affix said tail to said electric outlet in said position within said g oove.

7. A male electric plug as specified in claim 6,

wherein:

said ground pin member is hollow and pivoted on a pivot pin and said hollow ground pin member includes a spring pressed ball engaging said pivot pin for biasing said ground pin member into either rccumbant position in said groove or into position normal to the face of said plug.

8. A male electric plug having an electric ground, said plug being of the type having a pair of male prongs projecting from a front face connected to a pair of wires in a cable entering the rear face of the plug body,

the improvement comprising:

an electrically conductive socket, or tube, connected to the ground wire of said cable and extending through said body from an open end in said front face to an open end in said rear face; and

a ground pin of substantially greater length than the length of said socket, or tube, and slidably received therein for complete removal from the rear of said body, said pin having one end normally projecting from said front face parallel to said prongs and having a head at the other end thereof normally projecting from said rear face;

said head serving as a finger grip for withdrawing said prong freely and completely out of said body, from the rear thereof,

a second electrically conductive socket, or tube, connected to said ground wire and a second ground pin slidably received in said second socket for ground connection to an outlet plate.

9. In a grounding electric plug:

a plug body of predetermined axial length having an electrically grounded, open-ended socket extending the full axial length within said body;

an elongated ground pin of substantially greater length than said body and socket, freely and slidably received in said tube, said ground pin having one end projecting from said body in parallelism with the male prongs of said plug and having the other end projecting from said body to serve as a finger grip for withdrawal thereof from the rear of said plug; and

a second electrically grounded, open-ended socket, integral with said first mentioned socket and adapted to slidably receive a second ground pin for ground connection to an outlet plate. 

1. A male electric plug having an electric ground, said plug comprising: a plug body having a pair of male contact prongs projecting from one face thereof and having a three-wire electric cable secured in another face thereof, each of said prongs being connected to one of the wires of said cable; first grounding means including a pin receiving socket member in said body, an elongated ground pin member mounted to move relative to said socket and an electric conductor connecting one of said members to the third wire of said cable; and second grounding means, including an inflexible element immovably mounted on, integral with and grounded to one of said members of said first grounding means; and including a threaded fastening screw directly and inflexibly connecting said element to a female electric outlet.
 2. A male electric plug as specified in claim 1, wherein: said pin receiving socket member is a conductive sleeve extending through said body from said one face to said another face; said ground pin is freely and slidably received in said sleeve for complete withdrawal from said plug body; and said element of said second grounding means is a dead-end conductive sleeve integral with said pin receiving socket member.
 3. A male electric plug as specified in claim 1, wherein: said element of said second grounding means comprises a second pin receiving socket and said threaded fastening screw is a second ground pin having one end slidably received in said socket and the other end threaded to threadedly engage in the screw hole of said female electric outlet.
 4. A male electric plug as specified in claim 1, wherein: said pin receiving socket member is a hollow metal cylinder open at each opposite end for slidably receiving said ground pin; and said element of said second grounding means is a second socket closed at one end for slidably receiving a second ground pin, forming one end of said fastening screw.
 5. A male electric plug as specified in claim 1, wherein: said pin receiving socket member includes a groove in said body extending transversely of said one face between said male prongs, said ground pin member is pivoted at one end to said electric conductor to move from a position normal to said one face and parallel to said prongs to a recumbant position in said groove; and said element of said second grounding means is an integral tail on said pin.
 6. A male electric plug as specified in claim 1, wherein: said body includes a groove in said one face, said ground pin member is pivotable on said conductor from a position within said groove to a position normal to said one face; and said ground pin member includes an integral tail, having a threaded hole therein, for receiving said screw to affix said tail to said conductor in said normal position and to affix said tail to said electric outlet in said position within said groove.
 7. A male electric plug as specified in claim 6, wherein: said ground pin member is hollow and pivoted on a pivot pin and said hollow ground pin member includes a spring pressed ball engaging said pivot pin for biasing said ground pin member into either recumbant position in said groove or into position normal to the face of said plug.
 8. A male electric plug having an electric ground, said plug being of the type having a pair of male prongs projecting from a front face connected to a pair of wires in a cable entering the rear face of the plug body, the improvement comprising: an electrically conductive socket, or tube, connected to the ground wire of said cable and extending through said body from an open end in said front face to an open end in said rear face; and a ground pin of substantially greater length than the length of said socket, or tube, and slidably received therein for complete removal from the rear of said body, said pin having one end normally projecting from said front face parallel to said prongs and having a head at the other end thereof normally projecting from said rear face; said head serving as a finger grip for withdrawing said prong freely and completely out of said body, from the rear thereof, a second electrically conductive socket, or tube, connected to said ground wire and a second ground pin slidably received in said second socket for ground connection to an outlet plate.
 9. In a grounding electric plug: a plug body of predetermined axial length having an electrically grounded, open-ended socket extending the full axial length within said body; an elongated ground pin of substantially greater length than said body and socket, freely and slidably received in said tube, said ground pin having one end projecting from said body in parallelism with the male prongs of said plug and having the other end projecting from said body to serve as a finger grip for withdrawal thereof from the rear of said plug; and a second electrically grounded, open-ended socket, integral with said first mentioned socket and adapted to slidably receive a second ground pin for ground connection to an outlet plate. 